Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Malfunction Indicator Light (MIL)
MIL may also be referred to as CHECK ENGINE light. MIL is located in instrument panel. When ignition is first turned on, MIL should come on and remain on for 2-3 seconds to verify bulb and circuit operation, and then go off.
PCM monitors several different engine control system circuits. PCM is located in engine compartment. See PCM LOCATION table. If a malfunction occurs which affects vehicle emissions, a Diagnostic Trouble Code (DTC) is stored in PCM and PCM enters limp-in mode. In limp-in mode, PCM substitutes values for failed component to continue engine operation, but loss of good driveability may result. When DTC is stored in PCM, PCM will turn on MIL and MIL will remain on steady.
If PCM detects active engine misfire severe enough to cause catalytic converter damage, MIL will immediately turn on to warn driver of possible damage and DTC will be stored. On manual transmission vehicles, MIL will either flash or light continuously during an active engine misfire. On all vehicles, PCM will turn off MIL when malfunction is not detected during 3 consecutive engine misfire or fuel system monitor tests. PCM performs engine misfire and fuel system monitor tests within predetermined engine speed (RPM) and load operating conditions. MIL may be turned off by PCM, however, a DTC may remain stored depending on type of malfunction detected.
| Application | Location |
|---|---|
| TJ Body | On Firewall, Near Blower Motor |
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.